Pool cover

ABSTRACT

The pool cover is made of multi-layer light-weight construction having a translucent top layer to permit sunlight to pass through and an opaque bottom layer for absorbing sunlight passing through the translucent layer. In a two-layer construction, a plurality of pockets are formed in the bottom layer. In a three-layer construction, a plurality of pockets are formed in the intermediate layer. When in use, the opaque layer becomes heated by sunlight and transfers heat by contact to the water in the pool. The heated air in the pockets also serves to conduct heat to the water and to serve as a thermal insulating barrier during non-daylight hours. The top layer may also be made of reflective material to reduce heating of the water during short-term pool closures.

BACKGROUND OF THE INVENTION

[0001] This application is a continuation-in-part of copending application Ser. No. 08/180,423, filed Jan. 12, 1994. The applicants herein are also the inventors of U.S. Pat. No. 5,511,536, issued Apr. 30, 1996, for SOLAR-TYPE POOL COVER.

[0002] This invention relates to pool covers, and, in particular, solar pool covers. More specifically, this invention relates to pool covers useful for temporary or short-term closures of pools.

[0003] As is known, various types of pool covers have been employed for covering over swimming pools and the like. In some cases, a tarpaulin-like cover has been employed to cover over a swimming pool when the pool is not in use in order to prevent dirt and debris from falling into the water contained within the pool. Typically, these covers are of relatively light weight construction allowing fine-sized debris to enter the pool.

[0004] Other covers have been designed to close a pool for the season. This type of cover is placed over the entire pool including a small area around the perimeter to allow the placement of weighting means to hold the cover and place and to seal the perimeter to prevent dirt and debris from entering the pool. This type of cover is usually waterproof and collects rain water as well as debris on the top surface thereof, making removal of the cover difficult.

[0005] In cases where a swimming pool is heated, use has been made of covers which are constructed to retain as much heat as possible within the body of water within the pool. For example, some pool covers have used a combination of glass and aluminum in an attempt to conserve heat within the pool. However, the use of such materials can be dangerous while being difficult to handle. For example, there is a potential danger of glass breakage while the incompatibility of chlorine with aluminum dictates against the use of such a cover for swimming pool applications.

[0006] Other types of pool covers have been of a solar type. For example, U.S. Pat. No. 3,022,781 describes a heater made of plastic film layers wherein a lower layer is made absorbent to radiant energy by being painted black or by incorporating a black pigment within the plastic composition.

[0007] U.S. Pat. No. 3,072,920 (Yellott) describes a swimming pool cover for collection or reflection of solar heat in which the cover is made of a sheet of plastic material having a bottom surface covered with a layer of dark-colored material for the absorption of solar energy and an upper surface covered by a reflective surface, such as aluminum. In addition, an over-layer of transparent plastic material is attached to the marginal edge of the plastic sheet to form air-filled compartments or pockets to increase the buoyancy of the cover. In the summer, the cover is to be turned so that the dark absorptive surface is down facing the water with the aluminized surface facing the sky to reflect the sun's radiant energy. In the winter, the cover is to be reversed so that the dark surface is exposed to solar energy.

[0008] U.S. Pat. No. 3,893,443 (Smith) describes a floating pool heater comprising plural individual units, each capable of floating and having a bottom wall with a blackened surface on the inside. The units are rigid, being made of metal, fiberglass, or reinforced plastic resin.

[0009] U.S. Pat. No. 3,949,095 (Pelehach) describes a solar pool heating apparatus comprising plural individual units, each capable of floating and having a reflective bottom surface and transparent top surface.

[0010] U.S. Pat. No. 4,028,750 (Gustafsson) describes a pool cover having plural buoyancy cells, drainage apertures between the cells, and rigid reinforcing elements.

[0011] U.S. Pat. No. 4,146,015 (Acker) describes a solar pool heater which employs a membrane having a smooth side and a pebbled side wherein each of the pebbles is a sealed air pocket. The entire membrane is transparent to permit the transmission of radiant energy to heat the underlying water and pool bottom.

[0012] U.S. Pat. No. 4,426,995 (Wilson) describes a solar quilt intended primarily for agricultural purposes, although the use as a pool cover is mentioned. The quilt is described as having an upper film formed of semi-hemispherical modules which abut and are sealed to a lower film which is described as transmissive of downwardly directed solar radiation and reflective of upwardly directed radiant energy in the ultra-violet range. The lower film is said to be absorptive of incident solar energy. The lower layer is optionally made opaque through the use of metals or metal oxides applied to the surface of or throughout the layer. Metals and metal oxides would be inappropriate for use in a pool cover, since they are incompatible with chlorine. Wilson also recommends the use of strengthening materials or compartments running the length of the quilt. The construction of such a quilt, if placed on a pool, would permit free air flow under and through the quilt, which would cool the water as well as allowing entry of dirt and debris.

[0013] U.S. Pat. No. 4,709,688 (Paradis) describes an open cell pool cover intended for use with a water circulation system to allow flow of water through the pool cover. When the water circulation system is not in use, air would flow through these open cells which would cool the water as well as allowing entry of dirt and debris. Reference is made to previously known sealed cell pool covers which include an upper plastic sheet with dimples and a plastic sheet bonded to the upper sheet. Such a sheet would collect water, dirt, and debris on the top surface thereof.

[0014] Generally, the previously known structures are of relatively thick, heavy-weight construction. In those cases in which the covers which have been made of lightweight materials, the covers have tended to be of a transparent nature such that heat energy in a covered pool is permitted to radiate out of the pool through the cover during dark periods. Also, where the covers have been transparent, a portion of the radiant energy is reflected without being converted to heat to heat the pool water. Those covers which attempted to heat the water used a greenhouse effect, which promoted algae growth in and on the pool surfaces due to the passage of light into the water below the cover.

[0015] It has been known that a translucent or transparent cover will help heat a pool but that it also promotes algae growth and increases chemical usage to a point of danger to the user. While the pool cover of the present invention can be used to heat the pool, it does not employ a greenhouse effect. Moreover, it reduces algae growth and chemical usage.

[0016] The cover of the present invention forms an insulating barrier during periods of darkness, such as nighttime hours or cool day conditions, in order to conserve heat within a heated body of water within a swimming pool. This is accomplished in two ways. First, during sunlight hours, the heat rays of the sun impinging on the translucent or transparent top layer pass through and strike the bottom opaque layer and are converted to heat. The pool water then absorbs the heat either by contact with the opaque layer or through conduction from the super hot air trapped in the air pockets. Second, the pool cover serves to eliminate evaporation from the pool water while the cover is in place on the pool surface.

[0017] In another embodiment of the present invention for short term pool closures, the top layer is made reflective to prevent overheating of the pool and to further suppress algae growth.

[0018] During daylight hours, the opaque bottom layer of the pool cover blocks the light which is necessary for algae growth. Coupled with the evaporation preventing characteristics of the pool cover, the need for pool chemicals and water replacement is greatly diminished.

[0019] Accordingly, it is an object of the invention to provide a pool cover which has good insulating qualities with enhanced heat transfer into a body of water in a pool.

[0020] It is another object of the invention to provide a pool cover which is of lightweight construction and which can be easily handled.

[0021] Another object of the invention is to reduce or eliminate water evaporation.

[0022] It is yet another object of the invention to provide a pool cover which has an efficient heat transfer quality.

[0023] It is another object of the invention to provide a pool cover which eliminates algae growth while the cover is on a swimming pool.

[0024] It is yet another object of the invention to reduce the need for chemicals in maintaining a swimming pool.

[0025] It is still another object of the invention to provide a pool cover which can be made of recycled plastic materials.

[0026] It is still another object of the invention to provide a pool cover of low cost construction.

[0027] It is a further object of the invention to provide less filter run time with corresponding reduced pump run time which in turn reduces the amount of electric power needed.

[0028] It is a still further object of the invention to prevent dirt and debris from entering the pool water, both directly and during removal of the pool cover.

[0029] Yet another object of the invention is to provide a pool cover for short-term closure to keep a pool clean and easily restored to service.

[0030] Yet a further object of the invention is to eliminate filter run time and/or pump run time during a short-term closure of a pool and/or to eliminate the use of electricity during such closure.

[0031] Still a further object of the invention is to eliminate the need for chemicals during a short-term closure of a pool.

[0032] Still another object of the invention is to eliminate the need to drain and refill a pool for a short-term closure thereof.

[0033] Still another object of the invention is to keep the pool water cool during short term closures.

[0034] Yet another object of the invention is to reduce or eliminate the cost of pool maintenance during short term closures.

[0035] These and other objects and advantages of the invention will become more apparent from the detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036]FIG. 1 is a top view of a pool cover in accordance with the invention, in which the pool cover is disposed over a pool.

[0037]FIG. 2A is a cross-sectional view of a two-layer pool cover in accordance with the invention, in which the pool cover is floating on a body of water within a pool.

[0038]FIG. 2B is an enlarged view of a portion of a cross-section of a two-layer pool cover showing one row of encapsulated air pockets and the air pockets trapped between the pool cover and the water.

[0039]FIG. 2C is an enlarged view of a portion of a cross-section of a two-layer pool cover showing a first row of encapsulated air pockets and a second staggered row of encapsulated air pockets.

[0040]FIG. 3A is a cross-sectional view of a three-layer pool cover in accordance with the invention, in which the air pockets in the middle layer point towards the bottom layer.

[0041]FIG. 3B is an enlarged view of a portion of a three-layer pool cover showing one row of encapsulated air pockets and the air pockets trapped between the middle layer and the bottom layer.

[0042]FIG. 3C is an enlarged view of a portion of a three-layer pool cover showing a first row of encapsulated air pockets and a second staggered row of encapsulated air pockets.

[0043]FIG. 4 is an enlarged view of a portion of a three-layer pool cover in accordance with the invention, in which the air pockets in the middle layer point towards the top layer, and showing one row of encapsulated air pockets and the air pockets trapped between the middle layer and the top layer.

[0044]FIG. 5 is a cross-sectional view of an oversized three-layer pool cover in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0045] As shown in FIG. 1, a pool cover 10 is of rectangular shape (or shaped to fit the pool configuration) and is disposed in floating relation on a body of water (12 in FIGS. 2A-2C) within a pool 11. The pool cover may be of other shapes than rectangular and may be custom-shaped to the shape of a given pool. The cover is flexible and may be folded for storage when not in use. Alternately, a means 13 is positioned adjacent the pool 11 for winding of the pool cover 10 thereon when the cover is not in use. The description and function of the means 13 is set forth in detail in the specification and the drawings of application Ser. No. 08/180,423, filed Jan. 12, 1994, which disclosure is hereby incorporated by reference as if fully set forth herein.

[0046] In an embodiment shown in FIG. 2A, the pool cover 10 is of flexible construction and is made of two layers 14, 15. The construction of the pool cover is such that each layer may be made of a suitable lightweight plastic material, including without limitation polyvinylchloride, polystyrene, polyethylene, polypropylene. In addition, the overall pool cover is flexible so as to permit rolling up on itself or folding.

[0047] As shown in FIG. 2A and in enlargement in FIG. 2B, the pool cover 10 includes a first top layer 14 and a second bottom layer 15 secured to the first layer 14 in any suitable fashion, such as by bonding or the like, and preferably by heat welding. At least one of the layers (the bottom layer 15 in FIGS. 2A and 2B) has a plurality of pockets therein facing the other layer (the top layer 14 in FIGS. 2A and 2B) and which pockets are sealed relative to the other layer to encapsulate air therein.

[0048] In accordance with an embodiment of the invention, the top layer 14 comprises a translucent, or preferably transparent, layer for passing sunlight therethrough. The translucent or transparent layer 14 is of planar shape and is of a thickness of, for example, from about 1 to about 20 mils, preferably from about 1 to about 10 mils, and most preferably from about 1 to about 5 mils. The second layer 15 is opaque for absorbing sunlight passing through the translucent or transparent layer 14. The second opaque layer 15 is coextensive with the first layer 14, and of a thickness of, for example, from about 1 to about 20 mils, preferably from about 1 to about 10 mils, and most preferably from about 1 to about 5 mils. The choice of thicknesses is dictated by the desire for flexibility versus the desire for standing up to wear and tear. This compromise is best achieved by making the top translucent layer as thin as desirable and the bottom opaque layer somewhat thicker to handle the wear and tear during installation and removal and storage. Thus, for example, the top layer may desirably be 1 to 2 mils thick and the bottom layer may desirably be 2 to 4 mils thick. The cover 10 may be made of recycled plastic material, which is less costly. The opaque layer 15 may be made black in color, although any other dark color may be used. Thus, as illustrated in FIGS. 2A and 2B, it is the opaque layer 15 which has a plurality of pockets 16 formed therein in facing relation to the translucent or transparent layer 14. These pockets 16 are sealed relative to the translucent or transparent layer 14 so as to encapsulate air therein.

[0049] The pockets 16 may be of any shape, although semispherical or semiellipsoid or other shapes without corners are generally preferred. The pockets 16 may be of a variety of sizes to accomodate flexibility, handling, shipping, and storage requirements, but preferably the pockets 16 are at least ⅛ inch to an inch or more in diameter and at least ⅛ inch to a half inch or more in depth. The size, and particularly the depth, of the pockets is a factor to be considered in determining the thickness of the layer. Larger, and particularly deeper, pockets will require a greater thickness. As shown in FIG. 2C, the rows of pockets 16, 16 a are arranged in staggered fashion to permit trapping of air in the spaces 17 between the pockets 16 between the bottom layer 15 and the surface of the water 12. Preferably the diameter of the pockets is greater than the spacing between the pockets to provide greater contact with the water 12 in the pool.

[0050] The construction described is such that sunlight passing through the translucent or transparent layer heats the opaque layer 15 and the air in the pockets 16 and the opaque layer 15 conducts the heat to the pool water 12 under the opaque layer. The air sealed in the pockets 16 forms an insulating barrier for heat attempting to escape up through the cover 10, while the opaque layer 15 eliminates, or greatly reduces, the evaporation from the surface of the water 12 in the pool 11.

[0051] As shown in FIGS. 2A-2C, the encapsulated air pockets 16 are partially submerged in the water 12, so that additional air pockets 17 are formed between the bottom surfaces of the opaque layer 15 between the pockets 16 and the surface of the water 12. Again, it is noted that the rows of pockets 16, 16 a are in staggered relation, as shown in FIG. 2C, so as to create staggered pockets 17.

[0052] The pool cover 10 may be made in any suitable fashion. For example, a planar sheet of opaque material may be passed over a roller which has recesses therein, so that the pockets can be formed by being drawn into the recesses. Alternatively, the sheet of opaque material may be passed over a roller provided with projections of semi-spherical shape, for example, which serve to deform the sheet to form the pockets. Thereafter, a translucent or transparent layer and the formed opaque layer can be brought into mutual contact and sealed relative to each other so as to entrap air within the pockets 16. The resulting multi-layered sheet can then be cut into suitable widths, lengths, shapes, or desired configuration for the formation of the pool cover 10. A pool cover 10 may be made of one continuous piece or of multiple sections secured together in any suitable manner. Typically, in the manufacturing process, the lengthwise edges are flat (without pockets) for the outer ½ to 1 inch thereof. Thus, two sections may be joined by overlapping the flat lengthwise edges thereof and heat welding them together.

[0053] Since the pool cover 10 is of relatively light weight and flexible construction and because of the size and spacing of the pockets 16 in the opaque layer 15, when the cover 10 is rolled or folded, the pockets 16 retain their shape without collapsing. Further, since the cover 10 is made of plastic material having a planar upper surface, a minimum amount of water is retained on the cover 10 so as not to impede the folding or rolling of the cover 10.

[0054] When in use, the pool cover 10 is laid over the body of water 12 within the pool 11 during cool periods or during nighttime periods in order to conserve heat within the body of water 12. The pool 11 may optionally be of heated construction so that the water 12 can be heated to suitable temperatures for recreational or therapeutic purposes.

[0055] During daytime, sunlight which impinges on the pool cover 10 passes through the translucent or transparent layer 14 to heat the opaque layer 15, which in turn serves to transfer the heat to. the body of water 12 either by direct contact or through the heated air pockets 16 and 17. The pool 11 is optionally provided with recirculation equipment so that the hotter water at the top of the pool can be cycled to the bottom of the pool whereby the cooler water at the bottom of the pool rises to the top to be heated through use of the cover 10.

[0056] At the same time as the opaque layer 15 is being heated by sunlight, the air encapsulated within the pockets 16 and trapped in the pockets 17 is also heated, providing additional heat transfer to the water 12. During non-daylight hours, the encapsulated air in pockets 16 and trapped air in pockets 17 acts as a thermal barrier to the passage of heat upwardly through the cover 10. Thus, the heat from the opaque layer 15 and the body of water 12 is retarded from passing upwardly through the pool cover 10.

[0057] Since the opaque layer 15 serves to block passage of sunlight into the body of water 12, algae growth is inhibited in the water 12 and on the sides of the pool 11. This, in turn, leads to a reduction in the need for chemicals in the water 12 to suppress algae growth. Further, since the layer is opaque, there is no need to incorporate an ultraviolet light inhibitor in the plastic material of the layer.

[0058] Thus, the invention provides a pool cover 10 of relatively light weight, which can be readily wound up on itself or folded for storage purposes when not in use. The invention further provides a pool cover which can be readily manufactured and installed.

[0059] By way of example, a pool cover constructed as shown in FIGS. 2A-2C was compared with a conventional translucent aqua-colored bubble cover of known construction. Two four-foot round pools, each approximately one foot deep and equipped with a recirculating pump, were used for the comparison. A pool cover in accordance with FIGS. 2A-2C was placed over one pool (pool A) and the second pool (pool B) was covered with a conventional bubble cover. Both pools were subjected to the same sun and wind conditions.

[0060] The results obtained show that the new pool cover on pool A absorbed more heat than the conventional pool cover on pool B. Specifically, the water in pool A was found to be consistently 4 degrees F. warmer than the water in pool B. Moreover, the opaque layer in the test, which was black, inhibited the growth of algae compared to the conventional pool cover. And, the use of recycled materials reduced the cost of manufacture, while reducing pollutants.

[0061] A second experiment was conducted on algae growth using an 18-foot by 36-foot, deep hopper in-ground vinyl-lined pool. The chlorine, measured in parts per million (ppm), was allowed to drop to 0.2 ppm, and the temperature was raised to 90 degrees F. After forty (40) hours under these conditions, algae began to form on the vinyl liner of the pool. A pool cover in accordance with FIGS. 2A-2C (having a black opaque layer) was then placed on the entire water surface for forty-eight (48) hours. When the cover was removed, the algae that had been on the vinyl liner was no longer visible.

[0062] Thus, the invention provides a pool cover which greatly reduces the need for chlorine and algaecides, which in turn reduces the amount of pollutants released into the environment.

[0063] Still further, the use of the cover reduces the need for pump run time thereby saving electricity and increasing the longevity of the pump and pump motor.

[0064] In accordance with another embodiment of the invention, the top layer 14 comprises a reflective layer made of a plastic material, including without limitation polyvinylchloride, polystyrene, polyethylene or polypropylene, which has a reflective powder, including without limitation a silver powder, dispersed therein. Alternatively, the reflective layer may be made of a sutiable plastic, as described above, with a reflective coating, such as a silver coating, thereon. Yet another alternative is to make the reflective layer from a reflective plastic material such as Mylar, however, such materials tend to be relatively stiff and rigid and would inhibit rolling up or folding of a pool cover of any extended length. In all other regards, the structure of the pool cover is as described above.

[0065] This construction is particularly useful for short term pool closure up to several weeks without the need for daily maintenance. External heat, as from solar rays, is reflected away from the pool of water by the reflective layer. The reflective layer and the opaque layer inhibit algae growth as light is prevented from passing into the pool of water. There is a reduction in the water temperature, as well as a reduction of algae, water evaporation, and the need for chemicals. In addition, there is no need to run a pump or a filter. This construction is also of lighter weight and greater flexibility than the cover described in U.S. Pat. No. 5,511,536. For such a construction, storing the cover with the reflective surface facing outwards prevents sunlight from heating and decaying the pool cover and promotes a longer life thereof.

[0066] In an embodiment shown in FIG. 3A, the pool cover 110 is constructed of three layers 114, 115, 120, each made of plastic material as described above, each layer having a thickness from about 1 to about 20 mils, the top layer 114 and bottom layer 120 each being planar, the middle layer 115 being provided with pockets, and each layer being coextensive with the other layers.

[0067] As shown in FIG. 3A and in enlargement in FIG. 3B, the pool cover 110 includes a first top layer 114, a second intermediate layer 115 having pockets 116, said second layer 115 being secured to the first layer 114 in any suitable manner as described above so as to encapsulate air in the pockets 116, and a third bottom layer 120 secured to the surfaces of the pockets 116 of the intermediate layer 115 in any suitable manner as described above to further encapsulate air in pockets 121. This construction can be readily made by sandwiching the intermediate layer 115 between the first top layer 114 and the third bottom layer 120 in known manner. The construction of the pockets 116 in the intermediate layer is as described above with respect to FIGS. 2A-2C. As shown in FIG. 3C, the rows of pockets 116, 116 a are in staggered relation.

[0068] In accordance with an embodiment of the invention, the top layer 114 comprises a translucent, or preferably transparent, layer for passing sunlight therethrough. The second intermediate layer 115 also comprises a translucent, or preferably transparent, layer. The third bottom layer 120 comprises an opaque layer, so as to be heated by conduction via the sandwiched layer 115. The second intermediate layer 115 can be made of a non-translucent or opaque material, although such has been found to be less effective in heating water 112 in a pool 111. The top layer 114 may alternately be made of a reflective material, as described above.

[0069] The construction described is such that sunlight passing through the translucent or transparent layers 114, 115 heats the opaque layer 120 and the air in the pockets 116, 121 and the opaque layer 120 conducts the heat to the pool water 112 under the opaque layer. The air sealed in the pockets 116, 121 forms an insulating barrier for heat attempting to escape up through the cover 110, while the opaque layer 121 eliminates, or greatly reduces, the evaporation from the surface of the water 112 in the pool 111 and suppresses algae growth.

[0070] In an embodiment shown in FIG. 4, the pool cover 210 is constructed of three layers 214, 215, 220, each made of plastic material as described above, each layer having a thickness from about 1 to about 20 mils, the top layer 214 and bottom layer 220 each being planar, the middle layer 215 being provided with pockets, and each layer being coextensive with the other layers. In this embodiment, the air pockets 216 formed in the intermediate layer 215 are oriented in the opposite direction as in the embodiment of FIGS. 3A-3C. Thus, the intermediate layer 215 is sealed to the bottom layer 220 to encapsulate the air in pockets 216 and the top layer 214 is secured to the surfaces of the pockets 216 to further seal air in pockets 221. In all other respects, the construction and variations therein and the function of pool cover 210 are the same as described with respect to pool cover 110 of FIGS. 3A-3C.

[0071] As further shown in FIG. 4, the pool cover 210 is preferably provided with drainage holes 222 preferably in a uniform grid pattern. Such drainage holes are preferably provided in each embodiment described above, i.e., cover 10, cover 110, cover 210. The drainage holes are preferably placed through the air pockets, 16, 116, 216, and are placed in selective ones of said air pockets. For example, the drainage holes may be placed in one or more rows of air pockets at spaced intervals along the length of the pool cover. Thus, one row may have drainage holes and the next ten rows may not, and this pattern may be continued along the length of the cover. It has been found that for a pool cover for a 16′×32′ pool, it is useful to provide at least about 80 such drainage holes up to about 200 holes, although fewer or more may be used. Obviously, with larger covers, more holes are necessary. It is useful to provide holes at a density of about 1-½ to 4 per square yard.

[0072] These drainage holes reduce water on the top surface of the cover and promote drying, which reduces heat transfer due to the reduction of the evaporation process. Also, by keeping the top surface dry, debris and dirt is free to be blown off the cover in the same manner in which it is deposited on the cover. And, when the cover is removed or re-installed, the possibility of water containing dirt and debris flowing into the pool is reduced or eliminated. And, rolling or folding of the cover is facilitated due to the lack of water and debris and dirt thereon. This also reduces wear and tear on the cover and enhances the life of the cover. The drainage holes are preferably added after the manufacturing process and are preferably punctured rather than punched so that there is substantially no removal of the pool cover material thus minimizing any light seepage through the holes and also minimizing any transmission of dirt or debris through the holes.

[0073] As shown in FIG. 5, the pool cover 210 is preferably made oversized to the surface area of the water 212 in the pool 211 to permit edge portions 223 thereof to abut the side walls of the pool 211 preferably for several inches and preferably on four sides. This construction, which is preferably used with any of the embodiments, pool covers 10, 110, 210, inhibits dirt and debris from passing into the water and helps lock the cover in place. This construction also promotes longevity of the pool cover, since such covers tend to undergo some shrinkage with time.

[0074] In the three layer construction of covers 110 and 210, the bubble layer is sandwiched between two other layers and is thus protected so that a sand papering effect does not occur. As a consequence, the bubble layer can be made thinner than the exterior layers to reduce the weight and increase the flexibility of such a three-layer cover. For example, the bubble layer may have a thickness of 1 mil, while the outer layers may each have a thickness of 2 mils or greater.

[0075] Generally, the pool cover has a relatively light weight, from about 1 to about 10 pounds per hundred square feet and preferably from about 1 to about 8 pounds per hundred square feet.

[0076] It is also to be understood that the above-described arrangements are merely illustrative of the many possible embodiments which represent applications of the present invention. Numerous and varied other arrangements can readily be devised in accordance with the principles of the present invention without departing from the spirit and scope thereof. 

What is claimed is:
 1. A pool cover comprising a first flat upper translucent layer for passing sunlight therethrough; a second intermediate layer secured to said first layer, said second layer having a plurality of pockets therein facing said first layer sealed relative to said first layer to encapsulate air therein to form an insulating barrier over a pool surface; and a third underlying opaque layer secured to said second layer to encapsulate air therebetween to provide further insulation, to reduce evaporation from the pool surface, and to inhibit growth of algae.
 2. A pool cover as set forth in claim 1 wherein each layer is made of plastic and is flexible to permit folding or rolling of the pool cover.
 3. A pool cover as set forth in claim 1 in which said three layers are coextensive and wherein said layers are sealed together at the peripheral edges thereof.
 4. A pool cover as set forth in claim 1 in which said layers are coextensive and oversized relative to the pool surface whereby when installed on a pool surface, the peripheral edges thereof extend upwards along the sides of the pool.
 5. A pool cover as set forth in claim 1 further comprising a plurality of drainage holes in said layers for passing water therethrough, wherein said plural drainage holes are provided through selected ones of said pockets.
 6. A pool cover as set forth in claim 1 wherein at least one of said upper layer and said intermediate layer is transparent.
 7. A pool cover comprising a first flat upper reflective layer for reflecting external heat away from a pool surface; a second intermediate layer secured to said first layer, said second layer having a plurality of pockets therein facing said first layer sealed relative to said first layer to encapsulate air therein to form an insulating barrier over a pool surface; and a third underlying opaque layer secured to said second layer to encapsulate air therebetween to provide further insulation, to reduce evaporation from the pool surface, and to inhibit growth of algae.
 8. A pool cover as set forth in claim 7 wherein each layer is made of plastic and is flexible to permit folding or rolling of the pool cover.
 9. A pool cover as set forth in claim 7 in which said three layers are coextensive and wherein said layers are sealed together at the peripheral edges thereof.
 10. A pool cover as set forth in claim 7 in which said layers are coextensive and oversized relative to the pool surface whereby when installed on a pool surface, the peripheral edges thereof extend upwards along the sides of the pool.
 11. A pool cover as set forth in claim 7 further comprising a plurality of drainage holes in said layers for passing water therethrough, wherein said plural drainage holes are provided through selected ones of said pockets.
 12. A pool cover as set forth in claim 7 wherein said first upper layer is provided with a reflective coating on the top surface thereof to make said layer reflective.
 13. A pool cover as set forth in claim 7 in which metallic powder is distributed through said first upper layer to make said layer reflective.
 14. A pool cover comprising a first underlying opaque layer to inhibit growth of algae and to reduce evaporation from a pool surface; a second intermediate layer secured to said first layer, said second layer having a plurality of pockets therein facing said first layer sealed relative to said first layer to encapsulate air therein to form an insulating barrier over a pool surface; and a third flat overlying translucent for passing sunlight therethrough secured to said second layer to encapsulate air therebetween to provide further insulation.
 15. A pool cover as set forth in claim 14 wherein each layer is made of plastic and is flexible to permit folding or rolling of the pool cover.
 16. A pool cover as set forth in claim 14 in which said three layers are coextensive and wherein said layers are sealed together at the peripheral edges thereof.
 17. A pool cover as set forth in claim 14 in which said layers are coextensive and oversized relative to the pool surface whereby when installed on a pool surface, the peripheral edges thereof extend upwards along the sides of the pool.
 18. A pool cover as set forth in claim 14 further comprising a plurality of drainage holes in said layers for passing water therethrough, wherein said plural drainage holes are provided through selected ones of said pockets.
 19. A pool cover as set forth in claim 14 wherein at least one of said overlying layer and said intermediate layer is transparent.
 20. A pool cover comprising a first underlying opaque layer to inhibit growth of algae and to reduce evaporation from a pool surface; a second intermediate layer secured to said first layer, said second layer having a plurality of pockets therein facing said first layer sealed relative to said first layer to encapsulate air therein to form an insulating barrier over a pool surface; and a third flat overlying reflective layer secured to said second layer to encapsulate air therebetween to provide further insulation and to reflect external heat away from the pool surface.
 21. A pool cover as set forth in claim 20 wherein each layer is made of plastic and is flexible to permit folding or rolling of the pool cover.
 22. A pool cover as set forth in claim 20 in which said three layers are coextensive and wherein said layers are sealed together at the peripheral edges thereof.
 23. A pool cover as set forth in claim 20 in which said layers are coextensive and oversized relative to the pool surface whereby when installed on a pool surface, the peripheral edges thereof extend upwards along the sides of the pool.
 24. A pool cover as set forth in claim 20 further comprising a plurality of drainage holes in said layers for passing water therethrough, wherein said plural drainage holes are provided through selected ones of said pockets.
 25. A pool cover as set forth in claim 20 wherein said first upper layer is provided with a reflective coating on the top surface thereof to make said layer reflective.
 26. A pool cover as set forth in claim 20 in which metallic powder is distributed through said first upper layer to make said layer reflective. 